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From:   Shakeel Butt <shakeelb@google.com>
Date:   Tue, 31 Jul 2018 07:58:00 -0700
Message-ID: <CALvZod75t+uK=FDtpuBCMZCk7cb4vQMy7DpXQ53Aj7ZLiYsTQQ@mail.gmail.com>
Subject: Re: [PATCH 1/3] mm: introduce mem_cgroup_put() helper
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Roman Gushchin <guro@fb.com>, Linux MM <linux-mm@kvack.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        David Rientjes <rientjes@google.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Tejun Heo <tj@kernel.org>, kernel-team@fb.com,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>
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On Tue, Jul 31, 2018 at 1:45 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 30-07-18 11:00:58, Roman Gushchin wrote:
> > Introduce the mem_cgroup_put() helper, which helps to eliminate guarding
> > memcg css release with "#ifdef CONFIG_MEMCG" in multiple places.
>
> Is there any reason for this to be a separate patch? I usually do not
> like to add helpers without their users because this makes review
> harder. This one is quite trivial to fit into Patch3 easilly.
>

The helper function introduced in this change is also used in the
remote charging patches, so, I asked Roman to separate this change out
and thus can be merged independently.

Shakeel

> > Link: http://lkml.kernel.org/r/20180623000600.5818-2-guro@fb.com
> > Signed-off-by: Roman Gushchin <guro@fb.com>
> > Reviewed-by: Shakeel Butt <shakeelb@google.com>
> > Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Shakeel Butt <shakeelb@google.com>
> > Cc: Johannes Weiner <hannes@cmpxchg.org>
> > Cc: Michal Hocko <mhocko@kernel.org>
> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> > ---
> >  include/linux/memcontrol.h | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 6c6fb116e925..e53e00cdbe3f 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -375,6 +375,11 @@ struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css){
> >       return css ? container_of(css, struct mem_cgroup, css) : NULL;
> >  }
> >
> > +static inline void mem_cgroup_put(struct mem_cgroup *memcg)
> > +{
> > +     css_put(&memcg->css);
> > +}
> > +
> >  #define mem_cgroup_from_counter(counter, member)     \
> >       container_of(counter, struct mem_cgroup, member)
> >
> > @@ -837,6 +842,10 @@ static inline bool task_in_mem_cgroup(struct task_struct *task,
> >       return true;
> >  }
> >
> > +static inline void mem_cgroup_put(struct mem_cgroup *memcg)
> > +{
> > +}
> > +
> >  static inline struct mem_cgroup *
> >  mem_cgroup_iter(struct mem_cgroup *root,
> >               struct mem_cgroup *prev,
> > --
> > 2.14.4
> >
>
> --
> Michal Hocko
> SUSE Labs